This species may be better placed in the genus Allochrocebus (see, for example, Tosi et al. 2004), but it was treated in previous Red List assessments (1988 to 30 June 2008) under the genus Cercopithecus; it is now placed under Allochrocebus following Mittermeier et al. (2013). Two subspecies, C. preussi preussi and C. p. insularis, following Grubb et al. (2003) and Groves (2005).

This updated assessment was created to accommodate the taxonomic move from Cercopithecus to Allochrocebus.

Justification:
This species is listed as Endangered as it is believed to have undergone a decline exceeding 50% over the past ~27 years across its restricted range, mainly as a result of increasing habitat loss in the Nigeria/ Cameroon highlands and also from hunting.

This species has a restricted distribution in western Cameroon, eastern Nigeria, and on Bioko Island. It is most abundant in montane and sub-montane forest up to at least 2,500 m asl. Its range includes isolated patches of forest in the grasslands of the Cameroon Highlands.

This species is divided into two subspecies: A. preussi preussi, on the mainland, and A. p. insularis, which is restricted to Bioko Island.

There has been no comprehensive population survey of this species, except on Bioko where the species has undergone declines exceeding 55% over a 20-year period (1986-2006; Hearn et al. 2006). On the mainland, the species is uncommon and highly fragmented.

This species is found mainly in montane and submontane forest above 800 m, and on Bioko shows a preference for Schefflera forest (Gonzalez Kirchner 2004, Hearn et al. 2006). It is also more rarely found in lowland forest (e.g., to 450 in the Caldera on Bioko), and can occur in isolated forest patches in mountainous grasslands. They have semi-terrestrial habits and are found usually in the understorey of the forest. Little is known about feeding behaviour, but it is known to eat fruits, seeds, leaves, and flowers. This species lives in groups of 2-12 animals, consisting of a single male and several females with their young.

This species’ population size and distribution have been severely affected by habitat destruction and hunting. For example, Cameroon’s forests have been severely eroded by cultivation, fire and collection of wood for fuel. As a result, little montane forest remains in the mainland part of this species’ range. This species is highly susceptible to human predation because it is semi-terrestrial and relatively large-bodied, and hunting has led to a decline in its population across its range, but particularly on Bioko.

This species is listed as Class B under the African Convention, and under Appendix II of CITES. The species occurs in the Okwangwo division of Cross River National Park and on the adjacent Obudu Plateau (Nigeria), Pico Basile National Park and the Southern Highlands Scientific Reserve (Bioko), and in the Takemanda Forest Reserve, Ibo Forest, and Banyang-Mbo Forest (Cameroon) which has been proposed for elevated protection status. Surveys of the status and distribution across its range are needed. None of the montane forest areas of the Cameroon highlands, the most important remaining habitat for this species, are formally protected and require urgent conservation action.

In-Place Research, Monitoring and PlanningIn-Place Land/Water Protection and Management Occur in at least one PA:YesIn-Place Species ManagementIn-Place Education Included in international legislation:Yes Subject to any international management/trade controls:Yes